1. Fields of the Invention
The present invention relates to an image processing method, especially to a predictive coding method for coding texture features of images.
2. Descriptions of Related Art
Due to the improved coding efficiency of video compression standards, the video compression standards have been applied to various fields such as video telephony, video conferencing, video streaming, etc. Generally, the video coding technology involved in these applications such as H.264, a standard for video compression, consists of various techniques such as discrete cosine transform (DCT), motion estimation (ME), motion compensation (MC), quantization (Q), variable length coding (VLC), etc. In the quantization process, quantization parameter (QP) corresponding to quantization step—size is an adaptive and important coding parameter, having great effects on the quality of the coded video. Among the image compression techniques available now, the texture prediction is used for intra frame prediction. Moreover, for an image coding technique using adaptive bandwidth control, a predictive coding model is selected. By using texture data already coded in low resolution images as reference, following texture is predictable. There are two predictive coding models representing texture, including 16×16 intra prediction mode and 4×4 intra prediction mode. Thus the coding efficiency is improved and residue bits of the coding image are reduced.
In the 16×16 intra prediction mode, a macroblock includes 16×16 blocks. The intra 16×16 supports four prediction modes, Mode 0-vertical mode, Mode 1-horizontal mode, Mode 2-direct current (DC) mode, and Mode 3-plane mode. When the block sizes of the macroblock is 4×4(intra 4×4), the prediction modes is composed of 9 types, Mode 0-vertical mode, Mode 1-horizontal mode, Mode 2-direct current (DC) mode, Mode 3-diagonal-down-left mode, Mode 4-diagonal-down-right mode, Mode 5 -vertical-right mode, Mode 6-horizontal-down mode, Mode 7-vertical-left mode, and Mode 8-horizontal-up mode. However, while the above image compression techniques available now is used for coding the high-resolution images such as HD (high definition image) or full HD images, the computation complexity also increases along with the higher image quality.
Thus there is a need to provide a predictive coding method for coding texture features of images that uses neighboring macroblocks and distribution of macroblocks of low-resolution images as references for prediction. Moreover, a ratio between different predictive modes used in a single image frame can be set so as to improve image quality.